With the advance of medical technology, there are a number of medical prostheses and devices which are implantable in humans for re-constructive and/or cosmetic purposes. These include breast implants; penile implants; musculature and other soft tissue implants; pace makers; valves; artificial joints and limbs such as knees, shoulders, legs, fingers, etc.; pins; screws; plates; rods; nails and other braces and supports. In order to ensure the continued safety and health of patients receiving these implants, the Safe Medical Device Act of 1990 has been enacted which dictates that manufacturers of Class III implantable medical devices institute a device registry for tracking of their devices, notification of patients, and otherwise monitoring these implants after they have been placed in a patient. Compliance with this Act has been proposed through a method of tracking which requires the surgeon who implants the device to complete and return a form or card with patient demographic data and implant data to the manufacturer or to a third party registry service. This method requires careful accumulation of data by a surgeon or his staff as well as secure inventory control procedures in order to ensure that the data is properly associated with the correct implant. Additionally, there is a risk of loss of the data entirely resulting from misdirected or lost communications. Furthermore, access to this data can be impeded in the event of an emergency situation or other circumstances which interfere with a patient's ability to recall or report the proper information which medical personnel may then use to access the registry and data contained therein.
There have been some suggestions in the prior art of marking the implants themselves with, for example, a radiopaque marker or other marker which contains the information relating to the implant. Ideally, this data could then be viewable by X-ray or some other non-invasive manner. However, there are difficulties with these prior art approaches. First of all, a breast implant with a radiopaque marker would at least partially obscure or mask tissue which is desired to be viewed in order to detect artifacts relating to tumors or the like for diagnosing cancer. Obviously, this is highly undesirable as the incidence of breast cancer presents a significant risk to many females. Additionally, repeated exposure to X-ray is not generally considered healthful or desirable and represents at least an added inconvenience entailing some degree of expense to recall or access the implant data. Therefore, radiopaque markers have not been viewed as a suitable long-term solution to this problem.
In order to solve these and other problems in the prior art, and in order to provide a convenient, fool proof marker secured to the implant itself and yet readable in a non-invasive manner, the inventors herein have succeeded in designing and developing an implant which incorporates a passive transponder which may be encoded and subsequently accessed with a hand held electromagnetic reader in a quick and inexpensive procedure. The passive transponder may be secured to the implant by any convenient means. For example, in a breast implant, the multi-layered shell for the implant may be laminated around the transponder to thereby be permanently and securely fixed to the implant. The transponder may be laminated in the sidewall of the shell, or between layers which comprise the seal patch which is applied to the shell to seal the mandrel opening. Similarly, the transponder may be laminated onto the surface of most other implants in an unobtrusive location. In some other implants, the transponder may be inserted into a hole or inlay and sealed in place.
As passive transponders are commercially available in a cylindrical shape sized at 2 mm in diameter and 11 mm in length, the patient will not sense any discomfort or even the presence of the transponder. Also, the transponder may be encoded with any suitable encoding scheme. A commercially available transponder presently provides for the storage of up to 64 binary bits of data. This data capacity may accommodate the direct storage of much, if not all, of the information desired to be recorded and maintained in a device registry. Furthermore, the storage capacity of the transponder is expected to be increased as further development occurs over time. Alternately, a number, collection of numbers, combination of numbers and letters, or other indirect code may be stored which after reading may be used to access a data bank which itself contains the desired information. Of course, if information is directly stored in the implant, it becomes immediately available upon reading the transponder. This provides ready access to information in emergency situations. Alternately, with the widespread availability, accessibility, and use of computers over telecommunications networks including telephone lines, it is not generally considered to be unduly limiting to provide that the code read from the transponder be then used to access an appropriate data bank in order to obtain the patient demographics, manufacturer's name, date of manufacture, surgeon's name, date of implantation,
A companion hand held electromagnetic reader is also commercially available which emits a low frequency magnetic field to activate the passive transponder and thereby cause it to transmit its encoded data to the reader. With this particular commercial device, no battery or other source of electrical power need be included in the passive transponder. This further reduces the size required for the transponder and renders it particularly suitable to this application.
While the principal advantages and features of the present invention have been described above, a more complete and thorough understanding of the invention may be attained by referring to the drawings and description of the preferred embodiment which follow.